Heroin became the drug of choice for many opioid users:

Group of answer choices

around $1900,$ because it could be injected.

during the $1920$s$,$ because it was easier to smuggle the small amounts needed for an effective dose.

during World War II$,$ when supplies of raw opium were cut off.

in the $1960$s$,$ because users believed that it was more pure than other opioids.